They give a set amount of time to answer several questions verbally in front of a panel of 2-3 people. Treat them as if they know NOTHING about you for they usually don't before the interview as they want to see how you present yourself. (A human does NOT look at your application for skills and experience until after the interview is done.) Afterward you will be taken to a seperate panel of people who will judge you on a 1 on 1 scenario. Be polite and treat them just like you would a patron of the library. Greet them, ask what they need help with today, and remember to just guide the person though everything don't do anything for them!
After the hiring process is done if you didn't get a position do not be discouraged make sure to send an email asking what you could do better the next time. I was told that the questions for the first part should be spread out the whole time do not rush or limit your self try to up sell yourself or explain more. a good measure is to straight divide the time like if you have 10 questions and 1 hour to answer give keep talking for 6 mins to answer each question.